Lee,
For what it's worth, this is the poll construct I always use:
while (true) {
zmq_pollitem_t items [] = {
{ onesocket, 0, ZMQ_POLLIN, 0 }
{ twosocket, 0, ZMQ_POLLIN, 0 }
};
// Calculate timeout here or use 0 for infinity
int rc = zmq_poll (items, 1, mytimeout);
if (rc == -1)
break; // Always check for Ctrl-C
if (items [0].revents & ZMQ_POLLIN) {
zmsg_t *msg = zmsg_recv (onesocket);
if (!msg)
break; // Always check for Ctrl-C
// Process message
zmsg_destroy (&msg);
}
// Test all sockets (not an else here)
if (items [1].revents & ZMQ_POLLIN) {
...
}
// Do regular maintenance if needed
}
-Pieter
On Tue, Feb 19, 2013 at 11:04 PM, Lee Sylvester <[email protected]> wrote:
> Okay, so this brings me kinda to where I was before:
>
> int read_zmq_connections() {
> zmq_pollitem_t items [] = {
> { zmq_responder, 0, ZMQ_POLLIN, 0 }
> };
> errno = 0;
> int ret = 0;
> while ( errno == 0 ) {
> zmq_poll(items, 1, 0);
> if (items [0].revents & ZMQ_POLLIN) {
> char *str = s_recv(zmq_responder);
> add_remote_account(str);
> free(str);
> ++ret;
> } else {
> break;
> }
> }
> return ret;
> }
>
> So, I poll the events and, if an error occurs or if there is no event, then I
> return the number of messages retrieved. Have I missed something?
>
> Thanks,
> Lee
>
>
> On 19 Feb 2013, at 17:11, Charles Remes <[email protected]> wrote:
>
>> It looks better except for the use of "size" in the loop control. The return
>> code from zmq_poll is the *number of sockets* that have pending events. The
>> way you are using it appears as though you believe the return code indicates
>> the *number of messages* which is incorrect. The way the loop is written
>> now, it will loop once and exit at most.
>>
>>
>> On Feb 19, 2013, at 10:29 AM, Lee Sylvester <[email protected]> wrote:
>>
>>> Okay, thank you. So I now have the following:
>>>
>>> int read_zmq_connections() {
>>> zmq_pollitem_t items [] = {
>>> { zmq_responder, 0, ZMQ_POLLIN, 0 }
>>> };
>>> errno = 0;
>>> int ret = 0, size = zmq_poll(items, 1, 0);
>>> zmq_msg_t message;
>>> while ( size > 0 && errno == 0 ) {
>>> char *str = s_recv(zmq_responder);
>>> parse_new_data(str);
>>> free(str);
>>> ++ret;
>>> --size;
>>> }
>>> return ret;
>>> }
>>>
>>> I'm going to test it a little later once I've written my client code. :-)
>>>
>>> Thanks again.
>>>
>>> Cheers,
>>> Lee
>>>
>>>
>>>
>>> On 19 Feb 2013, at 16:21, Charles Remes <[email protected]> wrote:
>>>
>>>> Yes, you are missing out on being able to differentiate between reads &
>>>> writes since you aren't checking the revents. However, in your case you
>>>> only have a single socket and you only register for POLLIN, so you can
>>>> just use the return code and skip the hard stuff. Any time it returns 1
>>>> then you know that your socket is readable.
>>>>
>>>>
>>>> On Feb 19, 2013, at 10:18 AM, Lee Sylvester <[email protected]>
>>>> wrote:
>>>>
>>>>> Okay, thanks. I'm looking at the reference and I can see that zmq_poll
>>>>> returns the number of items, but it feels like I'm missing something when
>>>>> I rely on that :-S
>>>>>
>>>>> Lee
>>>>>
>>>>>
>>>>> On 19 Feb 2013, at 15:52, Charles Remes <[email protected]> wrote:
>>>>>
>>>>>> Hmmm, I'm not sure that's exactly right.
>>>>>>
>>>>>> The basic idea is that you want to check the return code from zmq_poll.
>>>>>> If it is greater than 0, then the socket can be read from. You should
>>>>>> then read from the socket until no more messages are available. I don't
>>>>>> know how it works with the #s_recv() function (presumably that is part
>>>>>> of the czmq binding) but you want to read until the socket is empty or
>>>>>> you get EAGAIN. Perhaps that function does that for you under the covers.
>>>>>>
>>>>>> So, the loop should be around reading from the socket and *not* around
>>>>>> zmq_poll. Does that make sense?
>>>>>>
>>>>>>
>>>>>>
>>>>>> On Feb 19, 2013, at 9:16 AM, Lee Sylvester <[email protected]>
>>>>>> wrote:
>>>>>>
>>>>>>> Thank you, that's great. So, based on what I've read, does this look
>>>>>>> correct for what I'm trying to accomplish?
>>>>>>>
>>>>>>> int read_zmq_connections() {
>>>>>>> zmq_pollitem_t items [] = {
>>>>>>> { zmq_responder, 0, ZMQ_POLLIN, 0 }
>>>>>>> };
>>>>>>> while (1) {
>>>>>>> zmq_msg_t message;
>>>>>>> zmq_poll(items, 1, 0);
>>>>>>> if (items[0].revents & ZMQ_POLLIN) {
>>>>>>> char *str = s_recv(zmq_responder);
>>>>>>> parse_new_data(str);
>>>>>>> free(str);
>>>>>>> } else {
>>>>>>> break;
>>>>>>> }
>>>>>>> }
>>>>>>> return 0;
>>>>>>> }
>>>>>>>
>>>>>>> Thanks,
>>>>>>> Lee
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> On 19 Feb 2013, at 14:52, Charles Remes <[email protected]> wrote:
>>>>>>>
>>>>>>>> Take a look at the man page for zmq_poll. You can do a non-blocking
>>>>>>>> poll for incoming messages on your socket. If it returns immediately
>>>>>>>> with 0, then no sockets in your pollset have pending messages to read.
>>>>>>>>
>>>>>>>> Be aware that when zmq_poll does indicate that you have messages, you
>>>>>>>> must read *all* of them from the socket before zmq_poll will work
>>>>>>>> again. I'm pretty sure the man page explains this.
>>>>>>>>
>>>>>>>> Good luck.
>>>>>>>>
>>>>>>>> On Feb 19, 2013, at 8:44 AM, Lee Sylvester <[email protected]>
>>>>>>>> wrote:
>>>>>>>>
>>>>>>>>> Hey guys,
>>>>>>>>>
>>>>>>>>> So, I've integrated ØMQ into my server. Now, I want to use ØMQ as a
>>>>>>>>> means to supply information to a HTTP server from a separate
>>>>>>>>> management app. So, in theory, it will look something like this
>>>>>>>>>
>>>>>>>>> int read_zmq_connections() {
>>>>>>>>> int ret = 0;
>>>>>>>>> while (zmq_has_messages(zmq_responder)) {
>>>>>>>>> char *str = s_recv(zmq_responder);
>>>>>>>>> parse_new_data(str);
>>>>>>>>> free(str);
>>>>>>>>> ++ret;
>>>>>>>>> }
>>>>>>>>> return ret;
>>>>>>>>> }
>>>>>>>>>
>>>>>>>>> This way, if there are no messages on zmq_responder, then the
>>>>>>>>> function will simply return. What I don't know how to do (and can't
>>>>>>>>> quite find) is how to check if messages exist on the connection. Can
>>>>>>>>> anyone please point me in the right direction?
>>>>>>>>>
>>>>>>>>> The reason why I need this non-blocking is that I will only be
>>>>>>>>> calling 'read_zmq_connections' approximately once every five minutes
>>>>>>>>> and I don't want my app to hang while waiting for messages.
>>>>>>>>>
>>>>>>>>> Thanks loads in advance,
>>>>>>>>> Lee
>>>>>>>>> _______________________________________________
>>>>>>>>> zeromq-dev mailing list
>>>>>>>>> [email protected]
>>>>>>>>> http://lists.zeromq.org/mailman/listinfo/zeromq-dev
>>>>>>>>
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